main() {
  var gifts = {
    // Key:    Value
    'first': 'partridge',
    'second': 'turtledoves',
    'fifth': 'golden rings'
  };

  var nobleGases = {
    2: 'helium',
    10: 'neon',
    18: 'argon',
  };
  print(nobleGases);
  print(gifts);

  gifts = new Map();
  gifts['first'] = 'partridge';
  gifts['second'] = 'turtledoves';
  gifts['fifth'] = 'golden rings';

  var d = {'name': 'fzx', 1: 'jonah'};
  print(d);

  print(d[1]);
  print(d['name']);

  d['name'] = 'fzx else';
  print(d);

  print(d[2]); //null

  print(d.length);
}
